SpringBoot＋ MDC实现全链路调用日志跟踪

MDC（Mapped Diagnostic Context，映射调试上下文）是 log4j、 logback及 log4j2提供的一种方便在多线程条件下记录日志的功能，基于ThreadLocal实现的一种工具类。

1、新增拦截器，统一处理trace问题（Constant.TRACE_ID = "traceId"）

先看MDC是否存在 traceId，有则不作处理，没有时再看header里是否有 traceId，没有的话则新生成并放置在MDC中，能解决接口请求，第三方调用，异步方法执行等场景，但线程存在丢失的情况

@Component
public class TraceIdInterceptor implements HandlerInterceptor {
 
    /**
     * 确保MDC有traceId
     * @param request
     * @param response
     * @param handler
     * @return
     * @throws Exception
     */
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        //如果有上层调用就用上层的ID
        String mdcTraceId = MDC.get(Constant.TRACE_ID);
        //MDC有traceId，直接返回
        if (StringUtils.isNotBlank(mdcTraceId)) {
            return true;
        }
        String headerTraceId = request.getHeader(Constant.TRACE_ID);
        //MDC没有traceId，从header取
        if (StringUtils.isNotBlank(headerTraceId)) {
            MDC.put(Constant.TRACE_ID, headerTraceId);
            return true;
        }
        //MDC、Header都没有则新生成
        MDC.put(Constant.TRACE_ID, TraceIdUtil.getTraceId());
        return true;
    }
 
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)
            throws Exception {
    }
 
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
            throws Exception {
        //调用结束后删除
        MDC.remove(Constant.TRACE_ID);
    }
 
}

public class TraceIdUtil {
 
    public static String getTraceId () {
        return UUID.randomUUID().toString().replaceAll("-", "");
    }
}

2、

@PostMapping("/pageList")
public Object list (@RequestBody ProductPage productPage) {
	IPage<Product> result = productService.pageList(productPage);
	final ResponsePage<Product> responsePage = new ResponsePage<>();
	BeanUtils.copyProperties(result, responsePage);
 
	//异步方法
	for (int i = 0; i < 2; i++) {
		new Asy().print(i);
	}
 
	HttpRequestUtil.doPost("http://127.0.0.1:9009/product/category/detail/1562264184600199170", MDC.get(Constant.TRACE_ID), new HashMap<>(), null);
 
	HttpHeaders headers = new HttpHeaders();
	headers.add("traceId", MDC.get(Constant.TRACE_ID));
	HttpEntity<String> requst = new HttpEntity<>(null, headers);
	RestTemplate restTemplate = new RestTemplate();
	restTemplate.postForObject("http://127.0.0.1:9009/product/category/detail/1562265011976994817", requst, Object.class);
}
 
@Slf4j
@Async
class Asy {
 
    public void print (int i) {
        try {
            Thread.sleep(1000L);
            log.info("异步 " + i);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

3、日志打印格式设置：%X{traceId}

    "CONSOLE_LOG_PATTERN"
              value="[${ServerIP}:${ServerPort}] %clr(%d{yyyy-MM-dd HH:mm:ss.SSS}){faint} %clr(%level){blue} %clr([traceId:%X{traceId}]){yellow} %clr([%thread]){orange} %clr(%logger){cyan} %m%n${LOG_EXCEPTION_CONVERSION_WORD:-%wEx}" />
    "CONSOLE_LOG_PATTERN_NO_COLOR" value="[${APP_NAME}:${ServerIP}:${ServerPort}] %d{yyyy-MM-dd HH:mm:ss.SSS} %level [traceId:%X{traceId}] [%thread] %logger %m%n${LOG_EXCEPTION_CONVERSION_WORD:-%wEx}" />

//使用线程池时，traceId将会丢失